Roadmapping is a term used to refer to a special type of angiographic fluoroscopy including multiple phases. In a first phase, acquired X-ray images are displayed as acquired without performing any image subtraction while a radiation dose applied to a patient is regulated. During a second phase, a contrast agent is injected into patient vasculature and a roadmapping mask image is generated by subtracting an image of anatomic background information from a sequence of image frames acquired with contrast agent introduced into vasculature and accumulated over the image sequence. During a third phase, a roadmapping mask image is used to guide the physician during an x-ray imaging examination without further contrast agent injection.
In known systems, in order to support a roadmap mode, an image post processing system such as the system of FIG. 1, acquires images in a first phase 11 and employs a temporary internal storage buffer 12 in which a mask frame is built using minimum gray luminance values of pixels of the acquired images during the second phase. At the end of the second phase the mask frame is moved to permanent storage 14 from the temporary storage so that an internal storage buffer can be used for other intermediate image processing functions. At the start of the third phase, the mask frame is read back to the internal buffer to be used as a mask frame that is subtracted from a live fluoroscopic image during third phase 16 to give a roadmap image. Known systems involve transfer latencies and delay in transferring image data between permanent storage locations of intermediate result buffers and memory accessible by image processing hardware. A system according to invention principles addresses these deficiencies and related problems.